Gelatinous or semigelatinous blasting explosives



Ratented Sept. 6, 1938 PATENT OFFICE GELATINOUS R BLASTINGSEMIGELATINOUS ExrLosIvEs Vernon Harcourt Williams, Ardrossan,

Ayrshire,

Scotland, and-Bernard William Foster, Blackheath, London,

Great Britain No Drawing. No. 90,002.

8 Claims.

This invention relates to gelatinous or semi-,

gelatinous blasting explosives containing a quantity of nitroglycerineor other liquid nitric ester gelatinized with a proportion ofnitrocellulose. In such explosive -.compositions oxidizing salts,

carbonaceous materials, nitro-compounds, explosive or power-producingsalts and cooling salts are often included for the purpose of modifyingthe properties of the compositions.

The invention relates particularly but not exclusively to gelatinous orsemi-gelatinous blasting explosives in which a proportion of coolingsalts or the like has been included for the purpose of rendering thesaid explosives suitable for use in i5 fiery or dusty mines. Suchexplosives will be referred to hereinafter as safety explosives.

The gelatinous or semi-gelatinous character of an explosive compositionis determined in part-by the proportion of liquid nitric ester and anyother :0 liquid ingredients, and in part by the proportion andabsorbency of any may be included in the composition. Common absorbentsso included are carbonaceous materials, e. g. woodmeal, and theseare'usually 5 characterized by a high absorbency. In gelatinousexplosives the structure of the gelatinized nitric ester is retained tosuch an extent that the mix constitutes a coherent jelly. Suchexplosives are normally cartridged by an extrusion 0 process. Insemi-gelatinized explosives, however, the structure is more or lessdiscontinuous; and the liquid ingredients are only partly absorbed bythe absorbent materials present and are distributed between theabsorbents and the nitrocellulose. 5 Such explosives are normally toostill in texture to be extruded. like fully gelatinized explosives. Theease with which an explosive composition can be cartridged, particularlyby an extrusion process, is dependent upon its plasticity; and I thisterm is used hereinafter to indicate those properties of the compositionby virtue of which it, can be worked under. pressure so that it assumesa coherent and compact form which, after deformation under pressure,does not regain its original shape when the pressure is released.

In both fully gelatinous and semi-gelatinous explosives it isadvantageous to increase the plasticity of a given composition, dueregard being paid to other requirements. Thus, for example, ingelatinous or semi-gelatinous explosive compositions it is known thatthe plasticity is largely accounted for by the proportion of nitrocompound or nitric ester present, but, although there must be present acertain minimum proportion of the said materials in order to aflord thenecessary England, Chemical Industries Limited Application In GreatBritain July 26, 1935 absorbent materials that assignors to Imperial acorporation of July 10, 1936, Serial sensitivity, too great a proportionis undesirable on the grounds of economy, risk of exudation, and reducedsafety. Moreover, a proportion of the nitric ester added may be absorbedby any unsaturated absorbent carbonaceous materials 5 present, anddifiiculty has been experienced hitherto, particularly when theexplosive compositions contain such materials, in obtaining a suitableincrease of plasticity without unduly increasing the proportion ofnitric-ester present.

The plasticity can also be increased by adding to the composition aproportion of a carbonaceous ingredient of low absorbency, such asstarch, but such an addition causes a decrease in the oxygen value ofthe composition. Dufliculty. has also been experienced hitherto inproducing safety explosives having bothsatisfactory plasticity andsatisfactory oxygen balance. As a large proportion of cooling salts mustbe included in these explosives and as the total proportion of salts islimited, it is not practicable to include more than a limited quantityof oxidizing salts, which may be insuflicient to balance the negativeoxygen value of 'the carbonaceous absorbents associated with the liquidnitric ester.

We have found that both the plasticity and safety of gelatinous orsemi-gelatinous blasting explosives of the kind described may beimproved by including in the composition a proportion of a clay or otherclq-like inorganic material as hereinafter describe either in additionto the other ingredients of the composition, or wholly or in part insubstitution for the carbonaceous absorbents which may be includednormally.

It will be understood that, whereas the increase in plasticity affordedby the present invention is of practical value throughout the entirerange of gelatinous and semi-gelatinous explosives, the improvement insafety is of practical value only when the compositions already 40contain suflicient cooling salts, or have been otherwise modiiied, tobring them within the recognized class of safety explosives.

Throughout the present specification and claims attached thereto, theterm plastic explosive shall be understood to refer to blastingexplosives of the gelatinous and semi-gelatinous types.

' The terms clay" or plastic clay as employed in the present applicationshall be understood to refer to a member of the class of plasticaluminum silicates, that is, those aluminum silicates which normallyexihibit plastic properties when in a finely divided state (whetheror'not containing other metals as well as aluminium or' other acidgroups as well as silicate as minor constituents 2 in theircompositions). The clays employed are preferably those having anabsorbency for nitroglycerine of the same order as that of starch.Amongst the clays that included, for instance, china clay, pipeclay, orbentonite. The clays are used in the finely divided state in which theynormally exhibit their plastic properties, and those of them that have ahigh afiinity for water, for example bentonite, may, if desired, beemployed in association with a small proportion of water but in theabsence of free water. The presence of water in such manner is often ofparticular advantage, since it improves the plasticizing properties ofthe clay, and since it is fixed by the clay there is no risk of the lossof sensitiveness which might otherwise occur if free water were presentin the mixture.

In putting the invention into effect, the quantity of the clay which wemay employ may depend on circumstances, but useful efiects areordinarily obtained with quite small quantities of the order of 2%-6%.In certain circumstances itmay be possible toincorporate largerquantities.

In general, the addition of a clay to a gelatinous or semi-gelatinousexplosive in accordance with the present invention increases theplasticity, and reduces the magnitude of the oxygen value,

(whether positive or negative) in proportion to the amount of clayemployed. It will be understood, however, that advantages of theinvention may also he realized in practice in that simultaneousmodifications in the nature and proportions of the other ingredients ofthe compositions for particular purposes may be made.

Thus, for example, in compositions containing a proportion of highlyabsorbent carbonaceous material a part or even the whole of suchcarbonaceous material may be replaced by the clay, and the resultingincrease in plasticity may be suflicient to convert the semi-gelatineinto a fully gelatinous .explosive. If, on the other hand,'it is desiredprimarily to reduce the proportion of liquid nitric ester, simultaneousreplacement of part of the carbonaceous ingredient by clay will enablethat to be effected without detriment to the plasticity, and with lessrisk of exudation. In both cases the final explosive will have anincreased oxygen value in comparison with the original composition. i

In the particular case of safety explosives, the increase in safetyspecifically attributable to the use of clay or clay-like material inthe preferred proportions is also of practical importance. The power ofthe explosive is, of course, reduced ac cording to the diluent effect ofthe clay, but the increase in safety more than compensates for thispower reduction. If, however, the clay is substituted for an equivalentproportion of cooling salts, the power and oxygen value of the explosiveare unaltered, and the safety increased.

The inventionis further illustrated by the following examples, in whichthe parts are "parts by weight.

Example 1 v Parts Nitroglycerine nitroglycol mixture- Nitrocotton 1.3Dinitrotoluene f 3 Ammonium nitrate 45.! Sodium nitrate 10 Bentoni 5Maize starch. 5

These ingredients were'incorporated in the normal manner, the clay andthe maize starch being may be employed are added together. Theplasticity of this explosive was about the same as an explosive madewith 10 parts of 'maize starch instead of the 5 parts of clay and the 5parts of starch, but the oxygen value per gm. of the unwrapped explosivewas +5.1 as against -0.5. When wrapped the corresponding values were'0.9 and 6.5. This example illustrates the improvement of oxygen valueat constant plasticity.

Example 2 Parts Nitroglycerine nitroglycol mixture 30 Nitrocotton 1.3Dinitrotoluene 3 Ammonium nitrate 55.7 Bentonite 5 Water, absorbed inthe bentonite 2 Maize starch 3 The oxygen value of this explosiveunwrapped was +5.0, and its explosive .listic mortar, was 80% power,tested by the bal- (blasting gelatine=100 Example 3 Parts Nitroglycerinenitroglycol mixture 25 Nitrocotton"- 0. 7 Dinitrotoluene 3.0Ammonium-nitrate 54.3 Sodium nitrate 7.0 Bentonite r 5.0 Maize star h5.0

The oxygen value of the unwrapped explosive was +5.5, the power 76% ofblasting gelatine, and the plasticity about the same as in Examples 1and 2.

I Example 4 Parts Nitroglycerine nitroglycol mixture 25 Nitrocotto 0.8Dinitrotoluene 3.0 Ammonium nitrate 46.2 Sodium chlor 18.0 Wheat flour-2.0 China clay- 5.0

The ingredients were mixed together as in the previous examples, and theexplosive was com pared with a s 'lar composition including the sameproportions of ingredients except that china clay was omitted and thesalt increased by a correspondingmmoun of the power of blastinggelatine, and an oxygen balance of +4.7. The composition containingchina clay, however, was the more plastic, and its safe charge limit ingas was 10 oz. as compared with 8 oz. for the explosive without chinaclay. This example shows the increase in safety of a safety explosiveobtained by the present invention.

We claim:

1. A plastic explosive composition comprising a liquid explosive nitricester, a gelatinizing agent for said nitric ester, and a plastic clay. r

2. A plastic explosive composition comprising a liquid explosive nitricester, a gelatinizing agent for said nitric ester, and from 2 to 6% of aplastic clay.

3. A plastic explosive composition comprising a liquid nitric ester ofan aliphatic alcohol con'-. taining at least two hydroxyl groups, agelatinizing agent for said liquid nitric ester, and a plastic clay.

4. The explosive composition of claim 3, in which the liquid nitricester comprises nitroglycerin.

5. The explosive composition of claim 3, in which the gelatinizing agentester comprises nitrocotton.

Each composition had 58% for the liquid nitric 1 6. A plastic explosivecomposition comprising nitroglycerin gelatinized by means ofnitrocotton,

and a plastic clay in an amount suflicient to impart improved plasticityand safety in the presence of inflammable gases.

7. A plastic safety explosive composition comprising nitroglycerin,nitrocotton, a cooling salt, and a plastic clay.

8. A plastic explosive composition comprising a liquid explosive nitricester, a gelatinizing agent for said nitric ester, and a plastic clay,said clay being associated with a small proportion of water,

free water being absent from said explosive com- 5 position.

.VERNON HARCOURT WILLIAMS. BERNARD WILLiAM FOSTER.

